Interconnections for electric assemblies typically include low reactance characteristics based on metal-to-metal contact; permanent interconnections being on the order of micro-ohms and disconnects being on the order of milliohms. Desirably, such interconnections have characteristics of stability in the presence of heat and time, of reproduceability from one interconnection to the next within a given process. The so-called permanent connections are achieved through processes such as soldering, welding, brazing, crimping, and wire bonding. Interconnections achieved through disconnect structures utilize relatively high pressure, spring brased interfaces frequently involving surface finishes employing noble metal plating thereon.
Interconnections of the disconnect type typically require normal forces on the order of 80 to 150 grams and frequently employ wiping action to eliminate surface oxides and/or dielectric debris. Forces of this magnitude, if applied in the form of wiping action, degrade the contact interface and limit the life or number of interconnects that can be made. The alternative is to utilize relatively thick coatings of precious metal, which practice is costly.
Interconnection of intelligence channels for intelligence transfer through digital or other signals can be accomplished magnetically as through the scanning of a magnetic medium such as a tape by magnetic head pickup. Optical techniques are also available wherein intelligence is transmitted as between phototransmitters and photoreceptors. Finally, as part of the background, a variety of techniques are employed utilizing radio frequency transmission, the so-called RF techniques widely employed through frequency modulation, audio amplitude modulation, and pulse code width modulation.
All of the foregoing have their advantages and applications, but all have certain shortcomings. Interconnections which require a physical metal-to-metal engagement under relatively high spring pressures and/or utilizing noble metals have quite limited lives in terms of the number of cycles of engagement possible and as well are vulnerable to the effects of moisture, industrial gases, and/or corrosive fluids and gases. Magnetic and optical techniques likewise are subject to environmental constraints. The optical techniques require a medium through which light can pass or at least a medium transparent to particular frequencies. The magnetic techniques require close proximity and are not readily sealable. RF devices are notably subject to interference such as static and field-caused noise.